RADIOFREQUENCY CATHETER ABLATION OF ECTOP IC ATRIAL TACHYCARDIAS - DIFFERENT MAPPING STRATEGIES TO LOCALIZE RIGHT AND LEFT-SIDED FOCI

Ectopic atrial tachycardia (EAT) is a rare form of supraventricular ta chycardia and often drug-resistant. Radiofrequency catheter (RFC) abla tion offers an alternative therapy suggesting a high efficacy rate. Lo calization of the EAT origin is proposed to be efficacious by various mapping strategies. We analyzed the efficacy of different mapping stra tegies for localization of right and left sided EAT foci. Methods and Patients: In a cohort of 48 patients (25 female; age 35 +/- 18 years) RFC ablation of 40 right and 12 left sided EAT foci was performed. Map ping of the right atrium was achieved with 2 ablation catheters using the ''encircling'' technique (Figure 1). We looked for an early bipola r local electrogram in relation to the onset of the P-wave and a QS-co mplex in the unipolar electrogram. The bipolar local electrogram was r etrospectively analyzed for a fragmented morphology and duration of mo re than 50 ms (Figure 3). In case of mechanical block of the EAT durin g mapping P-wave pace mapping over the mapping catheter was performed (Figure 4). Results: RFC ablation succeeded in 44 patients with 46 EAT foci (Figure 5). Left sided EAT origin was in 40% in the region of th e pulmonary veins. Two left sided foci were abladed within the coronar y sinus. An anteroseptal location in vicinity to the bundle of His was found in 4 cases (Figure 6). There were no differences between left a nd right sided origin regarding session duration (304 +/- 131 vs 241 /- 101 min) and fluoroscopic time (39 +/- 29 vs 31 +/- 19 min). The ac tivation time related to the onset of the P-wave was at successful abl ation site for left sided origin significantly earlier compared to a r ight sided origin (45 +/- 22 vs 30 +/- 18 ms). Fragmenation of the bip olar local electrogram was found before successful RFC application in 86% in the left and in 65% in the right atrium. The unipolar electrogr am showed in 87% of all cases a QS-complex before the successful RFC p ulse. In 16% a beat to beat change of the unipolar electrogram could b e found at successful ablation site (Figure 7). Both criteria had a lo w spe cifity and sensitivity. Mechanical block could be induced during mapping in 10 patients (20%). In these cases RFC application at a sit e with a perfect match of P-wave pace mapping succeeded in 8 patients. In 2 patients the same EAT occurred within the following 24 hours. Du ring a follow-up of 4 to 58 months there were additionally recurrence of EAT in 3 patients (3 to 6 months after ablation). No influence of t he AV nodal conduction was observed after ablation of anteroseptal EAT foci. Other acute or chronic complications were not observed. Conclus ions: 1. RFC ablation of right and left sided EAT foci is a safe: and efficacious treatment. There were no differences regarding session dur ation and fluoroscopic time between right and left sided foci. 2. Acti vation mapping showed an earlier activation time for left sided origin compared to right sided. 3. Mechanical block could be induced in 20% of cases. P-wave pace mapping might offer a strategy to localize the f ocus during mechanical block.